Old Tang | Pseudo-full-stack tech player: writes code without going bald, manages projects without going crazy, delivers without staying up late. No formal tutorials here, only a "slacking-off" practical manual that cures system pain points. Focuses on Shell, SQL, Java, and delivery, turning complexity into simplicity and making efficiency fun.
This guide explains how to create effective business architecture diagrams by focusing on roles, business domains, and end-to-end chains, using a four-layer structure to visualize capability boundaries and business flow rather than just listing functions.
This guide teaches how to create clear network topology diagrams by defining nodes, links, and paths, asking three key questions before drawing, choosing the right structure and annotations, selecting maintainable tools like Draw.io, and verifying accuracy against live configurations with a seven-point checklist.
This article explains why kill -9 fails to terminate Linux processes — covering guardian process restarts, uninterruptible D-state I/O waits, and zombie processes — and provides a systematic troubleshooting sequence for system-wide hangs: check disk space, OOM killer logs, and CPU vs I/O load before resorting to reboot.
This article explains how network isolation creates access boundaries but cannot protect against risks from exposed ports, detailing three port exposure risk categories, a case study of lateral movement via an internal SSH port, common production misconfigurations, and practical hardening steps including listening port audits, least-privilege firewall rules, secure Docker port mapping, and regular internal scanning.
This article details six common Docker and Kubernetes misconfigurations that enable container escape to host root within minutes, provides audit commands for Docker and K8s, and outlines hardening practices including capability dropping, non-root users, read-only filesystems, and runtime monitoring.
This article explains why df reports high disk usage while du shows much less, revealing that deleted files held open by processes consume space, and demonstrates how to identify and release these ghost files using lsof and /proc/pid/fd/ without restarting services.
A troubleshooting guide for intermittent TLS handshake failures across carriers, revealing how JDK default version differences cause protocol_version alerts and providing verification steps and fixes using -Dhttps.protocols=TLSv1.1,TLSv1.2 for Java, curl --tlsv1.2 for scripts, and Nginx ssl_protocols adjustments.
This guide explains why manually editing /etc/resolv.conf in Kubernetes Pods fails, details how kubelet generates DNS configuration via dnsPolicy and dnsConfig, and provides three solutions: modifying CoreDNS ConfigMap for cluster-wide fixes, per-Pod dnsConfig for exceptions, and correct dnsPolicy for hostNetwork Pods, plus the ndots:5 performance pitfall.
This article presents five native kubectl and Linux commands to systematically troubleshoot Kubernetes network connectivity issues — from pod-to-service DNS resolution and endpoint verification to host-level packet capture — enabling rapid root-cause identification without inspecting complex CNI configurations.
This tutorial teaches five native kubectl techniques for rapidly aggregating and filtering Kubernetes logs across multiple pods, including label selectors, time-based filtering, pod-prefix scripting, the kubetail tool for colored multi-pod streaming, and the --previous flag for crashed pods, plus a ready-to-use troubleshooting template.
